One of the accessories most widely used by bicyclists is a seat bag. Seat bags are usually attached to the seat by two straps, each of which wraps around one of the seat frame bars and is fastened by a buckle or hook and loop cloth (Velcro.RTM.), and a strap, also with a buckle or Velcro.RTM., that fastens the front end of the bag to the seat post. Recently, Cannondale Corporation introduced and is currently selling seat bags under the trademark "Seat Cleat.TM." that have a cleat member on the top of the bag that defines with a support member to which the bag is attached a pair of slots that face laterally outward away from each other and slidably receive the seat frame bars.
To attach a "Seat Cleat.TM." bag to the seat, the bag is inserted under the seat in a skewed orientation, pushed up so that the arms of the cleat member lie above the frame bars, and then rotated into the installed position, thereby bringing the frame bars into the slots. The "Seat Cleat.TM." bags also have a C-shaped clip at the front end. The clip has a pair of resilient legs that engage the seat post with one leg of the clip on either side of the post. The cleat member supports the bag vertically, and the clip keeps the bag from turning and from sliding lengthwise, which could allow the cleat member to become disengaged. The "Seat Cleat.TM." concept is disclosed in U.S. Pat. No. 5,127,563 (Chan et al. issued Jul. 7, 1992), which is owned by Cannondale and is incorporated herein by reference, and has the advantage of making it much easier to attach the bag to the seat and to detach it from the seat.
Heretofore, bicycle seat bags have usually been made from fabric. It is common to provide a stiffening insert, such as a sheet of semi-rigid polymeric film or foam, inside the fabric bag to impart shape to and enhance the load-carrying ability of the fabric bag. The manufacture of fabric bags is relatively labor-intensive, due to the need to stitch the bag from fabric components, attach a zipper or other closure, stitch the straps (when the bag has straps) and add other components, such as a reflector. Although fabric bags can be and usually are made of durable materials and last a long time, they are prone to soiling and to color-fading, so they eventually become somewhat unsightly. Water-repellant fabrics can be used, but fabric bags are not waterproof, and objects in the bag can become wet is the bag is left out in the rain or is placed on wet ground. Fabric bags provide relatively little protection to objects in the bag from impacts, particularly along the sides, and fragile articles in the bag can be damaged or broken by impacts to the bag.